JPH06109528A - Sound sorece searching system - Google Patents

Abstract

PURPOSE:To embody a sound source searching system having higher detection accuracy by providing two scan microphones, one reference microphone, and an operating means for locating a sound source. CONSTITUTION:Scan microphones M1, M2 are arranged with respect to a plane to which a sound source S belongs, i.e., a reproducing plane, and the scan microphones M1, M2 are moved horizontally on front and rear measuring planes MF, MR by means of a microphone traverse system TVS. Sound pressure outputs from the scan microphones M1, M2 and a fixed reference microphone M3 are amplified through amplifiers A1-A3. The sound pressure outputs thus amplified are then subjected to data conversion through A/D converters C1-C3 and further subjected to frequency region conversion through fast Fourier transform units FFT1-FFT3. Acoustic holography operation is then carried out at a holography operating section HD. In other words, the scan microphones M1, M2 are moved in parallel with the sound source S and sound pressure data of one scan microphone is expressed in terms of sound pressure data at the position of the other scan microphone assuming that the sound data has come from the direction of reproducing point and then the difference is subjected to weighting thus obtaining a synthesized sound pressure data. This operation is performed over the entire measuring plane thus locating the sound source.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound source search system, and more particularly to a device for searching the position and size of a noise generating source in a vehicle engine or the like.

[0002]

2. Description of the Related Art Conventionally, various methods for searching a sound source have been proposed. One of them has two scanning microphones arranged at a fixed interval of about 6 to 50 mm in front of and behind the sound source. Is installed in the near field of the sound source and the microphone output is obtained while moving both scanning microphones in parallel,
There is a method for obtaining the sound intensity of the sound source (“sound intensity method”).

In this system, a sound source is captured as acoustic energy flowing in a unit time in a unit time, and the average value of the sound pressures measured by both scanning microphones is p (t), and the particle velocity (a value proportional to the speed of sound, per unit distance. U (t)
Then, by measuring the vector quantity shown in the following equation (1) as the time average of the product of both, it is found that the sound source is located on the extension line of both scanning microphones where this vector quantity becomes maximum. To do.

[0004]

[Equation 1]

The particle velocity u (t) represents a change in phase.

In such a sound source search method based on the sound intensity method, since the measurement results at the scanning microphone measurement points are independent from each other, there is no correlation. Therefore, when the direction of the sound source is not parallel to the extension line direction of the microphone. There is a problem that a correct search cannot be performed.

Further, a sound source search method based on the "acoustic holography method" has been studied before the sound intensity method described above, and one microphone for scanning a measurement surface at a certain distance from the sound source and another The sound source is searched for by obtaining the sound pressure intensity and the phase of the two microphone output signals with the reference microphone fixed at one appropriate position.

Explaining this in a little more detail, in this method, as shown schematically in FIG.
By scanning horizontally and vertically on F, you can get the microphone output at each position.
The following reproduction formula (2) showing the back propagation formula of the sound wave propagation formula which is the basis for obtaining these microphone outputs while considering these microphone outputs and the sound pressure output of the reference microphone,

[0009]

[Equation 2]

Thus, the complex volume velocity amplitude Q (x, y, 0) of one point R (x, y, 0) on the reproduction surface (sound source surface) RF reproduced from the microphone M1 is obtained. However, the above formula
R in (2) is a point P (x, y, zo on the measurement plane MF.
) And a point R (x, y, 0) on the reproduction surface RF. Incidentally, P (x, y, zo) in the equation (2) represents the complex sound pressure output from the mac M1.

Then, when the microphone M1 scans the measurement surface MF in the horizontal and vertical directions, the complex volume velocity amplitude Q of one point R on the reproduction surface RF obtained by the output of each microphone position.
(X, y, 0) are all added, and the points R on the reproduction surface RF are taken as all the points on the reproduction surface RF and similarly the measurement surface M
By adding all the complex volume velocity amplitudes Q (x, y, 0) from F, the point with the largest amplitude Q is searched as the sound source.

FIG. 6 shows this point more specifically.
7 and FIG. 7, first, in FIG. 6A, the reproduction surface R
When the reproduction point R on F is reproduced as the sound source S, a sound picked up at the microphone position M1-1 of the microphone M1 and a sound picked up at the microphone position M1-2 are reproduced as shown in this figure. In the reproduced one, the sound wave propagation path and the back propagation path are equidistant and have the same phase. Therefore, as shown in FIG. 7A, the absolute value of the composite vector of the reproduced vectors (for example, Q1 to Q3). Is maximum when the reproduction point R on the reproduction surface RF is the sound source S, that is, at the position of the sound source S.

On the other hand, when the reproduction point R is reproduced at a position on the reproduction surface RF which is slightly deviated from the sound source S as shown in FIG. 6 (b), the microphone position M1-1 as shown in FIG. The back propagation path becomes longer during playback, and the microphone position M
In 1-2, the back propagation path during reproduction is shorter than the propagation path.

Therefore, there is a phase shift between the reproduced sound picked up at the microphone position M1-1 and the reproduced sound picked up at the microphone position M1-2.
As shown in, the composite vector (Q1
To Q3) are smaller than the combined vector shown in FIG.

By thus setting a large number of reproduction points R on the reproduction surface RF, when the reproduction point corresponds to the sound source position, the maximum combined vector is obtained as shown in FIG.
At other positions, the combined vector becomes small as shown in FIG. 7B, so that the sound source search is obtained in the former case.

[0016]

In the case of the sound source search using the acoustic holography method as described above, as shown in FIG. 7, the case shown in FIG. 7A and the case shown in FIG. There is a problem that the difference from the case shown is small and the detection accuracy of the sound source search is low.

Recently, a sound source search method based on the "near-field acoustic holography method" has been studied. This is a mode in which sound waves are linearly diffused from the sound source and propagated laterally from the sound source and attenuated at a short distance. The latter sound wave is also included in the search target, paying attention to the fact that there is a mode that causes
If the sound source is a heat generating device (for example, an engine manifold), the microphone cannot be installed at a close distance, which is not suitable for measurement.

Further, as an application example of the sound intensity method, in addition to two scanning microphones, one reference microphone is used, and the vibration mode of the sound wave propagating backward from the measurement surface and the emitted sound wave There is a "proximity particle velocity method" that predicts directivity and sound pressure level, but this method does not perform sound source search and cannot be used.

Therefore, it is an object of the present invention to realize a sound source search method with higher detection accuracy by improving the above acoustic holography method.

[0020]

In order to achieve the above object, in the sound source search method according to the present invention, at least two scanning microphones arranged in front of and behind the sound source and both scanning microphones are moved in parallel at the same time. Means, at least one reference microphone, and sound pressure data of the sound source from each microphone are input to assume that the sound pressure data of the first scanning microphone comes from the reproduction point direction. The sound pressure data at the position is converted, and the difference between the converted sound pressure data and the sound pressure data of the second scanning microphone is weighted to be combined with the sound pressure data of the second scanning microphone. The first
The calculation means for searching the position of the sound source by performing the measurement on the entire measurement surface of the scanning microphone.

[0021]

1 and 2 are conceptual diagrams for explaining the sound source search method according to the present invention in an easy-to-understand manner. At least two scanning microphones M are provided on the surface to which the sound source S belongs, that is, the reproduction surface.
1 and M2 are arranged in the front-back direction, and these scanning microphones M
1 and M2 are moved in parallel at the same time, and the microphone output at each point is given to the computing means.

In the calculation means, for example, assuming that the complex sound pressure P2, which is the output of the microphone M2 on the rear measurement surface MR, comes from the direction of the reproduction surface RF, the complex sound pressure P2 at the position of the microphone M1 on the front measurement surface MF. 'Is converted, for example, according to the following equation (3).

[0023]

[Equation 3]

It should be noted that r1 and r2 indicate the distances from the microphones M1 and M2 to the reproduction point R on the reproduction surface RF, respectively, and these are the distance Zo between the front measurement surface MF and the reproduction surface RF which is known in advance. And the distance ΔZ between both measurement surfaces can be obtained. Further, the front measurement plane MF and the rear measurement plane MR may have a relationship opposite to the above.

The complex sound pressure P2 'thus converted does not match the complex sound pressure P1 actually measured by the microphone M1 when the reproduction point R is not the sound source point.

Therefore, since the two sound pressures P1 and P2 'are complex numbers as shown in the following equation (3), since they can be expressed as shown in FIG. 3, the microphones M1 and M2 are derived from the complex sound pressures P1 and P2'. The composite complex sound pressure P3 of is calculated by, for example, the following equation (4).

[0027]

[Equation 4]

By applying the complex sound pressure P3 thus obtained to P (x, y, zo) of the above-mentioned reproduction equation (2), as in the conventional acoustic holography method, as shown in FIG. )
And a composite vector as shown in (b) is obtained, and the reproduction point of the largest composite vector becomes the sound source point.

At this time, since the coefficient α (for example, 6 to 60) is multiplied by the difference (P1−P2 ′) of the measurement data in the above equation (4) to perform weighting, the complex sound pressure P1 and When P2 'does not match, the complex sound pressure P3 has a larger phase shift as shown in FIG. 7 (c), and thus the composite vector is obtained by the conventional acoustic holography method shown in FIG. 7 (b). Since the value is smaller than the combined vector, the accuracy of detecting the sound source point is improved. It is also conceivable that the coefficient α becomes a variable depending on the position of the reproduction point R, for example.

The first and second scanning microphones may correspond to either the front or rear measurement surface.

[0031]

FIG. 4 shows an embodiment of a sound source search system according to the present invention. In this embodiment, two scanning microphones M1,
An M2 and a fixed reference microphone M3 are used, and these scanning microphones M1 and M2 are arranged in front of and behind the sound source S, respectively, on the front measurement plane MF and the rear measurement plane MR by the microphone traverse device TVS. The support rods B1 and B2 are attached so as to be horizontally moved. still,
Since the support rod B1 can move on the support rod B2, the scanning microphones M1 and M2 are eventually scanned on the front measurement plane MF and the rear measurement plane MR in the horizontal and vertical directions, respectively. .

Scan microphones M1 and M2 and reference microphone M3
After being amplified by amplifiers A1 to A3, the respective sound pressure outputs are converted into data by A / D converters C1 to C3 in the front processor FP, and similarly, fast Fourier transformers FFT1 to FFT in the front processor FP.
After being converted to the frequency domain by the FT3 (this is for obtaining the correlation), the above-mentioned acoustic holography calculation is performed by the holography calculation unit HC in the computer PC such as a personal computer or a workstation to display the display D such as a CRT or plotter. The sound source distribution map will be displayed on.

The controller CNT for controlling the microphone traverse device TVS is also a computer PC.
The moving speed of the microphone traverse device TVS controlled by the controller CNT is adjusted in advance to the speed at which the outputs of the microphones M1 to M3 are sampled. .

[0034]

As described above, according to the sound source search method according to the present invention, at least two scanning microphones are arranged in front of and behind the sound source and are moved in parallel at the same time, so that the sound of one scanning microphone is generated. By assuming that the pressure data came from the reproduction point direction and converting it to sound pressure data at the position of the other scanning microphone, the difference between the two is weighted to obtain the synthesized sound pressure data, which is applied to the entire measurement surface. Since it is configured to search for the position of the sound source by performing the search for the sound source position, it is possible to detect the sound source position with high accuracy without being restricted by the size of the measurement surface or the distance between the measurement surface and the sound source surface.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the operation principle of a sound source search system according to the present invention.

FIG. 2 is a perspective view showing a sound source and a measurement surface of a sound source search system according to the present invention.

FIG. 3 is a vector diagram showing a complex sound pressure calculated by a sound source search method according to the present invention.

FIG. 4 is a diagram showing an embodiment of a sound source search system according to the present invention.

FIG. 5 is a diagram for explaining sound pressure reproduction by a conventional acoustic holography method.

FIG. 6 is a diagram showing a state in which a sound source is reproduced by a conventional acoustic holography method.

FIG. 7 is a diagram showing a combined vector on a reproduction surface obtained by the present invention and a conventional example.

[Explanation of symbols]

 M1, M2 Scanning microphone M3 Reference microphone S Sound source MF Front measuring surface MR Rear measuring surface TVS Microphone traverse device FP front processor PC computer In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. At least two scanning microphones arranged in front of and behind the sound source, a means for moving both scanning microphones in parallel at the same time, at least one reference microphone, and sound pressure data of the sound source from each microphone. Is input to convert the sound pressure data of the first scanning microphone into sound pressure data at the position of the second scanning microphone on the assumption that the sound pressure data comes from the reproduction point direction, and the converted sound pressure data and the second scanning The position of the sound source is searched by weighting the difference with the sound pressure data of the microphone and synthesizing it with the sound pressure data of the second scanning microphone, and performing this for the entire measurement surface of the first scanning microphone. A sound source search method, comprising: